Try to link SSE/AVX code in arm64 kernel when cross compile from x86_64 host

[12101111]

System information

Type	Version/Name
Distribution Name	Gentoo Linux
Distribution Version	2.17
Kernel Version	6.13 rc6
Architecture	arm64/x86_64
OpenZFS Version	2.3.0 rc5

Describe the problem you're observing

When cross compile from x86_64 for arm64, zfs_config.h contains those flags:

/* Define if host toolchain supports AVX */
#define HAVE_AVX 1

/* Define if host toolchain supports AVX2 */
#define HAVE_AVX2 1
...
/* Define if host toolchain supports SSE */
#define HAVE_SSE 1

/* Define if host toolchain supports SSE2 */
#define HAVE_SSE2 1

/* Define if host toolchain supports SSE3 */
#define HAVE_SSE3 1

/* Define if host toolchain supports SSE4.1 */
#define HAVE_SSE4_1 1

/* Define if host toolchain supports SSE4.2 */
#define HAVE_SSE4_2 1

/* Define if host toolchain supports SSSE3 */
#define HAVE_SSSE3 1

The comment say those flags are for host, not for target

But in (zfs_fletcher.c)[https://github.com/openzfs/zfs/blob/master/module/zcommon/zfs_fletcher.c#L176], those flags are used for kernel code.

Describe how to reproduce the problem

./configure KERNEL_LLVM=1 KERNEL_ARCH=arm64 KERNEL_CROSS_COMPILE=aarch64-unknown-linux-gnu- --with-config=kernel --enable-linux-builtin
./copy-builtin /usr/src/linux

Then enable CONFIG_ZFS=y and compile kernel

make ARCH=arm64 CROSS_COMPILE=aarch64-unknown-linux-gnu- LLVM=1 LLVM_IAS=1 -j32

Include any warning/errors/backtraces from the system logs

  AR      built-in.a
  AR      vmlinux.a
  GEN     .tmp_initcalls.lds
  LD      vmlinux.o
  OBJCOPY modules.builtin.modinfo
  GEN     modules.builtin
  GEN     .vmlinux.objs
  MODPOST Module.symvers
  UPD     include/generated/utsversion.h
  CC      init/version-timestamp.o
  KSYMS   .tmp_vmlinux0.kallsyms.S
  AS      .tmp_vmlinux0.kallsyms.o
  LD      .tmp_vmlinux1
ld.lld: error: undefined symbol: fletcher_4_sse2_ops
>>> referenced by __efistub_vsprintf.c
>>>               vmlinux.o:(fletcher_4_impls)

ld.lld: error: undefined symbol: fletcher_4_ssse3_ops
>>> referenced by __efistub_vsprintf.c
>>>               vmlinux.o:(fletcher_4_impls)

ld.lld: error: undefined symbol: fletcher_4_avx2_ops
>>> referenced by __efistub_vsprintf.c
>>>               vmlinux.o:(fletcher_4_impls)

ld.lld: warning: <internal>:(.eh_frame) is being placed in '.eh_frame'
make[2]: *** [scripts/Makefile.vmlinux:77: vmlinux] Error 1